Display devices have been developed from cathode ray tubes (CRTs) using an accelerated electronic beam to plasma display panels (PDPs) based on plasma discharge, and liquid crystal displays (LCDs) using liquid crystal having an electro-optical effect. Besides, there are vacuum fluorescent displays (VFDs) using an electronic beam accelerated at a low speed, electro luminescent displays (ELDs), and magnetic liquid display panels. These display devices are classified into an active display device, which radiates light by itself, and an inactive luminescent display device, which requires a light source because the display device cannot emit light by itself.
LCDs, which are recently used for laptop computers, are representative of inactive luminescent display devices, are compact and light and consume a small amount of power. Accordingly, LCDs are widely used in compact electronic products as well as lap-top computers. Such LCDs have the above-mentioned merits, but also have the demerit that its manufacturing process is complicated due to the use of liquid crystal. In particular, in order that air bubbles do not remain on a liquid crystal layer existing between a front plate and a rear plate, which are a predetermined distance apart from each other, liquid crystal injection is performed by a complicate vacuum injection method using a differential vacuum pressure. The cavities of unit LCDs must be isolated from one another by partitions with certain widths in order to receive liquid crystal injected in a vacuum environment by the above-mentioned vacuum injection. Accordingly, when a large-screen display device is manufactured with several unit LCDs, the junction portion between adjacent unit LCDs occupies a significantly large effective area because of the partitions with certain widths. This degrades the continuity of an image on the unit LCDs. Also, LCDs must be formed of a material endurable against high heat since they undergo a high-temperature process. In addition, a complicated manufacturing process makes it difficult to produce large LCDs.
Like LCDs, magnetic liquid display panels are also classified into a non-emissive display device. As well known, magnetic fluid (ferromagnetic fluid) is a suspension in which superfine ferromagnetic particles are stably dispersed within a liquid. The ferromagnetic particles are not separated from the liquid under a general centrifugal force or a general magnetic field. A magnetic fluid is a magnetic colloid, which operates like having a magnetism within a magnetic field. The type of Magnetic fluids includes oxide magnetic fluid and metallic magnetic fluid. An example to which such magnetic fluid is applied is disclosed in European Patent No. 0633488 A1, in which a display panel adopts a principle similar to that of existing LCDs.
To be more specific, as shown in FIG. 1, magnetic fluid 4 is interposed between a front plate 1 and a rear plate 2. a plurality of magnetic field coils 3 for applying a magnetic field to the magnetic fluid 4, in which geometrically anisotropic magnetic particles are dispersed, are installed behind the rear plate 2. the magnetic field coils 3 are coupled to a display controller 5 for driving the magnetic field coils. The magnetic field coils 3 are also provided in a structure where loop-shaped patterns stacked on a multi-layered substrate are connected to one another by through holes. In such a display panel, as shown in FIG. 2, the magnetic particles at portions ON, which are supposed to transmit light 6, are aligned by the application of a magnetic field to the portions ON, thus transmitting light. Meanwhile, portions OFF, in which magnetic particles are naturally scattered, are supposed to absorb or block light.
However, it is extremely difficult for the magnetic particles in the magnetic fluid used in such a conventional display panel have geometric anisotropy in a superfine state. Also, light control based on the alignment or non-alignment of magnetic particles is not smooth. In addition, the magnetic field coils 3 for applying a magnetic field to magnetic fluid must be formed in a multi-layered structure, thus requiring a very complicated manufacturing process.
In a magnetic fluid display panel disclosed in U.S. Pat. No. 3,863,249, instead of using the alignment or nonalignment of magnetic fluid, light transmission is blocked or allowed depending on the presence or absence of magnetic fluid within a light transmission area due to the movement of magnetic fluid by a magnetic force. However, this magnetic fluid display panel requires a strong magnetic field to move magnetic fluid, and accordingly requires high energy. Also, the magnetic fluid display panel is very inferior in terms of pixel switching responsivity of the magnetic fluid, hence it is not suitable to form moving pictures. In addition, since the magnetic fluid display panel adopts magnetic coils as a magnetic field forming unit, the miniaturization of cells, and mass-production are difficult, and the manufacturing costs are high.
The inventor of the present invention has proposed a new magnetic fluid display panel through U.S. Pat. No. 5,912,652, in order to overcome the defects of such conventional magnetic display panels.
The aforementioned magnetic display panel can provide moving pictures with a fast responsivity, and also can be easily manufactured at a low cost in large quantities because of its simple structure. Furthermore, this magnetic display panel is significantly advantageous in the construction of super-large display devices by multiple integration. The present invention provides a magnetic display panel improved in performance based on such a magnetic display panel described above.